Shubha Maha Shivaratri

ॐ त्र्यम्बकं यजामहे सुगन्धिं पुष्टिवर्धनम् ।
उर्वारुकमिव बन्धनान् मृत्योर्मुक्षीय मामृतात् ॥

Om Tri-ambakam Yajaamahe Sugandhim Pushti-Vardhanam ।
Urvaarukamiva Bandhanaan Mrtyor-Mukssiiya Maa-[A]mrtaat ||
– Rig Veda 7th Mandala, 59th Sukta, 12th Shloka

Meaning of Mahamrityunjay Mantra:

Om, we worship the Three-Eyed One (Tryambaka / Shiva), who is fragrant (i.e. spiritual essence), increasing the nourishment (of our soul);
Just the way cucumbers fall from the plants when they mature, may we be liberated from the bondage of worldly matters, may we be liberated from cycle of death and birth (material attachment), so that we are not separated from immortality (eternal presence of the soul).

This Mantra was created by Vashishtha Rishi (Sage Vashishtha) and was dedicated to Rudra Devata (Shiva).